Polypyrrol (PPy) ist ein typischer Vertreter der intrinsisch leitfähigen Polymere und wird auf zahlreichen Gebieten, wie Analytik, Korrosionsschutz oder Elektrotechnik angewendet. Dabei nutzt man die elektronische Schaltbarkeit, die Stabilität und die gute Oxidierbarkeit sowie die Wasserlöslichkeit der Monomere aus. Im Rahmen dieser Arbeit wurde der Einfluss verschiedener Parameter, wie Temperatur, Monomerkonzentration und Leitsalz, auf die elektrochemische Polymerisation von Pyrrol untersucht. Des Weiteren sollte die Wirkung eines statischen Magnetfeldes auf die Synthese und das Ionenaustauschverhalten überprüft werden. Als Messverfahren kamen die elektrochemische Quarzmikrowaage (EQCM) und die elektrochemische Impedanzspektroskopie (EIS) zum Einsatz. Bei der Auswertung der EQCM-Daten wurde ein von Efimov entwickeltes mathematisches Modell zur Bestimmung des komplexen Schermoduls angewendet. Dadurch war eine in situ Verfolgung der viskoelastischen Eigenschaften während der Abscheidung und des Ionenaustausches möglich. Um den hydrodynamischen Einfluss auf die Synthese von PPy zu untersuchen, wurden Messungen an einer rotierenden Scheibenelektrode durchgeführt. Die daraus gewonnenen Erkenntnisse vermittelten eine Vorstellung, wie sich eine durch den magnetohydrodynamischen Effekt hervorgerufene Rührung auf die Grenzströme der potentiostatischen Abscheidung verschiedener PPy|Leitsalz Systeme auswirkt. Ferner ist die Abscheidung von PPy aus Phosphorsäure betrachtet worden, da diese Schichten eine Relevanz für den Korrosionsschutz besitzen.

Made available in DSpace on 2016-06-02T20:01:03Z (GMT). No. of bitstreams: 1 DissCMM.pdf: 1152867 bytes, checksum: 285bcaac4403e13affd7a9ae146f523c (MD5) Previous issue date: 2005-10-26 / This work intented to realize a study about the situation of process of Environmental Impact Assessment (EIA) in São Paulo State, with emphasis in the monitoring pos-EIS (Environmental Impact Statment) phase, that it is essencial for the efficiency and efficacy of EIA. The purpose was to evaluate the frequency that the monitoring is realized, which are the methods used, what the efficiency, the negative points and the difficults to execution of this system. For that, it was realized a bibliography revision about national and internacional practices of EIA, with research at libraries of Secretaria de Meio Ambiente do Estado de São Paulo (SMA), Companhia Estadual de Saneamento Ambiental (CETESB), Departamento de Avaliação de Impacto Ambiental (DAIA) and USP, and researches on data base. It were made interviews with technicals directors of DAIA/SMA and was also elaborated a questioner, that approach some points of EIA practices in São Paulo State. This questioner was sent to professionals of area. The results evidenced that despite of monitoring pos-EIS is very impotant in the context of EIA, it is not executed in the most of the cases. Many failures are pointed out in the process, which results in the non aplication of monitoring pos-EIS. The lack of engagement with the environmental quality and the sustainability, the lack of structure in the environmental agencies, the bureaucratic and consequent slowness of the process, the little participation of community, the difficulty in getting material about the topic, and others are some of factors mentioned. If the procedure were not improved, for assure the accomplishment of terms and commitments defined, as well as the learning with mistakes and the rights of each case, a powerfull instrument of Environmental Policy would be discredited and turn on in one of numerous bureaucratic obstacles that difficult the access on natural resourses of the country, but are not efficient to assure that the improvement happens in benefit of society. / Este trabalho teve como objetivo realizar um estudo da situação do processo de Avaliação de Impacto Ambiental (AIA) no estado de São Paulo, enfatizando a fase de monitoramento pós-Estudo de Impacto Ambiental (EIA), que é essencial para a eficiência e eficácia da AIA. Pretendeu-se avaliar com que freqüência o monitoramento é realizado, quais os métodos utilizados para sua realização, qual sua eficiência, seus pontos falhos e quais as dificuldades de operacionalização deste sistema. Para tanto, foi realizada uma revisão bibliográfica sobre práticas nacionais e internacionais de AIA, com consultas às bibliotecas da Secretaria de Meio Ambiente (SMA), Companhia Estadual de Tecnologia de Saneamento Ambiental (CETESB), Departamento de Avaliação de Impacto Ambiental (DAIA) e da USP e pesquisas em banco de dados. Foram feitas entrevistas com diretores técnicos do DAIA/SMA e também foi elaborado um questionário, que aborda alguns pontos de práticas de AIA no Estado de São Paulo. Este questionário foi enviado para profissionais da área. Como resultado, foi constatado que, apesar de muito importante no contexto da AIA, o monitoramento pós-EIA não é praticado na maioria dos casos. Muitas são as falhas apontadas no processo, que acabam culminando na não aplicação do monitoramento pós-EIA. A falta de comprometimento com a qualidade ambiental e a sustentabilidade, a falta de estrutura dos órgãos ambientais, a burocratização e conseqüente lentidão do processo, a baixa participação da sociedade, a dificuldade em se conseguir material sobre o assunto, entre outros, são alguns dos fatores mencionados. Se os procedimentos não forem aperfeiçoados, de modo a garantir o cumprimento dos termos e compromissos definidos, bem como o aprendizado com os erros e acertos de cada caso, um poderoso instrumento de política ambiental poderá ficar desacreditado e converter-se em apenas mais um dos já numerosos entraves burocráticos que dificultam o acesso aos recursos naturais do país, mas não são eficazes para assegurar que seu aproveitamento se dê em benefício da sociedade.

Biossensores que empregam dispositivos de efeitos de campo podem ser obtidos em diversas arquiteturas, incluindo dispositivos Eletrólito-Isolante-Semicondutor (EIS), que são capacitores em que o eletrodo metálico é substituído por um filme e uma solução. Medindo-se a capacitância em função do potencial aplicado, é possível detectar variações de pH oriundas de reações ou interações entre o filme e o analito. Nesta dissertação, sensores foram produzidos com a adsorção de filmes automontados de dendrímero (PAMAM) e nanotubos de carbono (SWNT) num chip. Medidas de espectroscopia de impedância foram realizadas para investigar o crescimento de cada bicamada do filme automontado, e os dados foram analisados com circuitos equivalentes que continham uma capacitância de dupla camada, um elemento de fase constante e uma capacitância para a região de depleção. Para o chip, os melhores ajustes foram obtidos na frequência de 2 kHz, em que a concentração de dopantes foi 6,6x1020 m-3 para o chip com isolante de SiO2 e de 1,1x1021 m-3 para o chip com isolante de SiO2/Ta2O5. O potencial de banda plana foi -0,2 V e -0,06V, respectivamente. Para os chips recobertos com os filmes de PAMAM/SWNT, observamos que a região de depleção é causada pelas cargas positivas do PAMAM. Com relação às implicações para biossensores, verificamos que o desempenho ótimo deve ser obtido com 3 bicamadas de PAMAM/SWNT. Isso pode explicar a observação empírica na literatura de que existe uma espessura ideal dos filmes para um desempenho otimizado. / Biosensors based on field effect devices can be produced with several architectures, including Electrolyte-Insulator-Semiconductor (EIS) devices, which are capacitors where conventional metal electrodes are replaced by a sensing layer and an electrolyte solution. By measuring the capacitance as a function of the bias voltage, it is possible to detect pH changes that may originate from reactions or interactions between the film in the sensing unit and the analyte. In this study sensors were obtained by adsorbing layer-by-layer (LbL) films made with dendrimers (PAMAM) and carbon nanotubes (SWNT) on a semiconductor chip. Impedance spectroscopy measurements were performed to monitor the growth of each bilayer in the LbL film, whose data were analyzed with equivalent circuits containing a double-layer capacitance, a constant phase element and a capacitance for the depletion region. The results for the semiconductor chip could be best fitted for a frequency of 2 kHz, where the doping concentration was 6.6 x1020 m-3 for the insulating SiO2 layer and 1.1 x1021 m-3 for the SiO2/Ta2O5 layer. The flat band voltage was -0.2 V and -0.06 V, respectively. In the analysis of the chip coated with different numbers of PAMAM/SWNT bilayers, we found that the depletion region appears as a contribution from the positive charges in the PAMAM layer. With regard to implications for biosensors, we found that optimized performance should be reached with three PAMAM/SWNT bilayers, which may explain the empirical finding in the literature that an ideal thickness exists for enhanced performance.

Lead-acid accumulators are the oldest and most common type of secondary cells. There are still some problems to solve. Grid corrosion in sulphuric acid is one of them, which reduced lifetime of lead-acid accumulators. The first part of work is focusing on a general theoretic description of lead – acid accumulators. Following is a description of the workstation and method of measuring. The final part of the text is measuring on an experimental cell.

The aim of this master’s thesis is electrochemical characteristics evaluation of magnesium alloys. The theoretical part describes the properties of magnesium and its alloys and their corrosion characteristics. In the experimental part are presented results of corrosion resistance measurement of two types of wrought magnesium alloys. It was AZ31 and AZ61 magnesium alloys, which were measured in Hank’s solutions with addition of ions Ca2+ and Mg2+ (SBF+) and without addition of the ions (SBF). The solution temperature during the measurement was 37 ± 1 °C. The experiments were used electrochemical impedance spectroscopy (EIS) and potentiodynamic tests using linear polarization (LP). EIS measurements were done in times of 5 minutes, 1, 2, 4, 8, 12, 24, 48, 72, 96 and 168 hours. Potentiodynamic tests were only short-term and they started after 5 minutes of stabilization. Both methods were used for measuring the electrochemical characteristics of polished and ground surface of the samples. The most important measurement results were polarization resistance, corrosion potential and corrosion current density. The electrochemical measurements are used to estimate the chemical composition influence and alloy’s structure of the corrosion resistance.

Pour répondre aux besoins de la miniaturisation des systèmes électroniques nomades, le monde du stockage de l’énergie a dû se réinventer et proposer des solutions innovantes permettant de répondre à ces problématiques. Parmi ces solutions, les microbatteries tout-solide « lithium-free » offrent de nombreux avantages (intégration facilité, aspect sécuritaire), malgré une cyclabilité encore limitée. L’objectif de cette thèse consiste à étudier ces microbatteries LiCoO2/LiPON/Cu, notamment par caractérisation électrochimique, pour en comprendre les mécanismes et proposer des solutions permettant d’en améliorer les performances. L’étude des couches unitaires de ce système a permis d’identifier les propriétés principales de chaque film mince et de connaitre la composition chimique et structurale de ces couches. Puis, la mise en place d’un protocole de charge servant à améliorer considérablement la tenue en cyclage a été décryptée à l’aide de la spectroscopie d’impédance électrochimique et de l’XPS. Ce travail a permis la compréhension fine des mécanismes physico-chimiques présent à chaque étape et de décrire un scénario quant au fonctionnement de ce protocole. Par ailleurs, la compréhension de ces phénomènes a été utile pour proposer des solutions permettant d’augmenter encore la tenue en cyclage des microbatteries Li-Free, pour que celle-ci puisse atteindre une capacité initiale et une cyclabilité équivalente aux microbatteries au lithium métallique, utilisé conventionnellement en microélectronique. / To meet the needs of the miniaturization of mobile electronic systems, the world of energy storage has had to reinvent itself and propose innovative solutions to meet these problems. Among these solutions, all-solid "lithium-free" microbatteries offer many advantages (easy integration, safety aspect), despite their still limited cyclability. The objective of this thesis is to study these LiCoO2/LiPON/Cu microbatteries, in particular by electrochemical characterization, in order to understand their mechanisms and propose solutions to improve their performances. The study of the unit layers of this system made it possible to identify the main properties of each thin film and to know the chemical and structural composition of these layers. Then, the implementation of a charging protocol to significantly improve cycling performance was decoded using electrochemical impedance spectroscopy and XPS. This work allowed the detailed understanding of the physico-chemical mechanisms present at each stage and to describe a scenario as for the operation of this protocol. In addition, understanding these phenomena has been useful in proposing solutions to further increase the cycling resistance of Li-Free microbatteries, so that it can reach an initial capacity and cyclability equivalent to lithium metal microbatteries, used conventionally in microelectronics

Polypyrrol (PPy) ist ein typischer Vertreter der intrinsisch leitfähigen Polymere und wird auf zahlreichen Gebieten, wie Analytik, Korrosionsschutz oder Elektrotechnik angewendet. Dabei nutzt man die elektronische Schaltbarkeit, die Stabilität und die gute Oxidierbarkeit sowie die Wasserlöslichkeit der Monomere aus. Im Rahmen dieser Arbeit wurde der Einfluss verschiedener Parameter, wie Temperatur, Monomerkonzentration und Leitsalz, auf die elektrochemische Polymerisation von Pyrrol untersucht. Des Weiteren sollte die Wirkung eines statischen Magnetfeldes auf die Synthese und das Ionenaustauschverhalten überprüft werden. Als Messverfahren kamen die elektrochemische Quarzmikrowaage (EQCM) und die elektrochemische Impedanzspektroskopie (EIS) zum Einsatz. Bei der Auswertung der EQCM-Daten wurde ein von Efimov entwickeltes mathematisches Modell zur Bestimmung des komplexen Schermoduls angewendet. Dadurch war eine in situ Verfolgung der viskoelastischen Eigenschaften während der Abscheidung und des Ionenaustausches möglich. Um den hydrodynamischen Einfluss auf die Synthese von PPy zu untersuchen, wurden Messungen an einer rotierenden Scheibenelektrode durchgeführt. Die daraus gewonnenen Erkenntnisse vermittelten eine Vorstellung, wie sich eine durch den magnetohydrodynamischen Effekt hervorgerufene Rührung auf die Grenzströme der potentiostatischen Abscheidung verschiedener PPy|Leitsalz Systeme auswirkt. Ferner ist die Abscheidung von PPy aus Phosphorsäure betrachtet worden, da diese Schichten eine Relevanz für den Korrosionsschutz besitzen.

A nickel alloy with high chrome and molybdenum content was found to form a highly resistive and passive oxide layer. The donor density and mobility of ions in the oxide layer has been determined as a function of the electrical potential when alkaline water layers are on the alloy surface in order to account for the relative inertness of the nickel alloy in corrosive environments.

There is huge academic interest and clinical need associated with the development of biomarker immunoassays where general aims are the generation of highly specific, convenient and sensitive sensing formats. In this project, a powerful electrochemical technique, electrochemical impedance spectroscopy (EIS), is applied in the establishment of powerful biomarker detecting protocols. Firstly, ultrasensitive, label-free and reusable insulin sensors, based on an antibody-PEGylated thiol self-assembly monolayer (PEG thiol SAM) interface, were produced and characterised via Faradaic EIS, presenting a detection limit (LOD) of 1.2 pM, a linear range across four orders of magnitude, and high sensitivity in even 50 % serum. By applying similar surface chemistry, a label-free biosensor, specific for the detection of α-synuclein antibodies, was fabricated. The α-synuclein interfaces used enabled the reliable detecting of this biomarker in patient sample serum. The concentration levels in the control and a patient group were determined to be significantly different, and, significantly, this difference was consistently across two different cohorts. Strikingly, this could potentially underpin an entirely new means of early Parkinson’s disease (PD) diagnosis. Non-Faradaic EIS methods were additionally applied to label-free insulin assays at both PEG thiol SAM and zwitterionic polymer film interfaces. The latter presented not only an exceptionally non-fouling interface, but also one seemingly both highly biocompatible and facilitating enhanced receptor: target binding. Finally, impedance assays, though potent, generally, operate by sampling only one of a limited number of available experimental variables, typically, Rct for Faradaic EIS, or C or Z for non-Faradaic EIS. Work carried out herein also explores the generation and utility of a portfolio of mathematically derived immittance functions all obtained from the same raw data sets. A particular focus was the examination of whether these were capable of increasing assay sensitivity and efficiency above normal impedance treatments.

Micro- and nano-electrodes have distinct advantages over large electrodes, including their decreased iR drop and enhanced mass transport due to radial diffusion characteristics which leads to the ready establishment of a steady state (or near steady-state) signal without convection. This enhanced mass transport also leads to increased current densities and signal to noise ratios. However, there is a need for fabrication techniques which reproducibly give micro- and nano-electrodes of controlled size and shape. The optimisation of systematic arrays on the nano-scale, open up possibilities for developing highly sensitive electrode devices, for use in physical chemistry and the determination of fast electrode kinetics and rates of reaction, as well as to provide highly sensitive electroanalytical devices, able to detect very low concentrations of substrates. This thesis first presents work involving the fabrication and characterisation on silicon substrates of square platinum microelectrodes. There is already an established theory for the behaviour of microdisc electrodes however, it is easier to make microsquares reproducibly using pixellated photomasks. The voltammetric and ac impedance characteristics of these electrodes in background electrolyte and in the presence of ferri/ferrocyanide redox couple are presented and the response is theoretically analysed. A combination of computer simulation, theory and experimentation show that these electrodes have increased current densities (14% greater) compared with a microdisc of equivalent radius and an alternative theoretical expression is presented to calculate the limiting current of microsquares at all dimensions. This thesis then discusses the development and optimisation of novel nano-band cavity array electrodes (CaviArE), using standard photo-microlithographic techniques. The resulting architecture encloses a Platinum nanoband of 50 nm width within each array element that is positioned half way up the vertical edges of shallow square cavities (depressions), with a total depth of 1050 nm. The width of the square cavity and the separation of the array elements can be controlled and systematically altered, with great accuracy. The CaviArE devices are shown to give quantitative pseudo-steady-state responses characteristic of multiple nanobands, whilst passing overall currents consistent with a macroelectrode. The array has a much enhanced signal-tonoise ratio compared with an equivalent microsquare array, as it has 0.167% of the area and is therefore markedly less affected by non-Faradaic currents, while it passes comparable Faradaic currents. At high sweep rates the response is also virtually unaffected by solution stirring. The impedammetric characteristics presented show different diffusional regimes at high, medium and low frequencies, associated with diffusion within individual square cavities, outside of the cavity and finally across the whole array as the diffusional fields of the neighbouring array elements overlap. Justification and fitting of equivalent circuits to these frequency regions provide details about the charge transfer, capacitance and diffusional processes occurring. The results show that these systems are highly sensitive to surface transfer effects and a rate constant for ferricyanide of 1.99 cm s-1 was observed, suggesting fast kinetic processes can be detected. Together, these characteristics make nanoband electrode arrays, with this architecture, of real interest for sensitive electroanalytical applications, and development of devices for industrial application is currently being undertaken.